Abstract: Novel phosphoric esters of the general formula ##STR1## in which X represents a halogen, R.sub.1 represents a linear or branched alkyl, fluoroalkyl or alkenyl group having from 1 to 36 carbon atoms, or a phenyl group substituted with a linear or branched alkyl group having from 1 to 15 carbon atoms, R.sub.2 represents an alkylene group having 2 or 3 carbon atoms, n is a value of from 0 to 30, and M represents a hydrogen atom, alkali metal, alkaline earth metal, ammonium, or an alkylamine or alkanolamine salt are prepared by reacting a salt of a phosphoric monoester of the general formula (II) ##STR2## in which R.sub.1, R.sub.2 and n have, respectively, the same meanings as defined above, and M.sub.1 represents an alkali metal, with an epihalohydrin of the general formula (III) ##STR3## in which X has the same meaning as defined above, and optionally, converting the resulting product into a free acid or a different salt.